The invention relates to a seat valve.
Seat valves with a spherical valve element are known. With such valves a leakage-free sealing can be effected but a positive switching overlap cannot be implemented without additional steps. In three-way seat valves in which a working connection is selectively connectable to a fluid connection and a tank in certain cases a positive switching overlap is desired. Thus, for example whilst the valve element is being switched over the passage from the fluid connection to the working connection is not to be freed until the passage between the working connection and the tank has been shut off.
According to an earlier application (P 36 10 693) the valve ball is guided in a bore of a valve insert, a sealing action resulting between the equator of the ball and the bore. This is employed for positive switching overlap in that the connection between the working connection opening centrally into the bore and the fluid connection or the tank is not released or shut off respectively until the ball has moved beyond the working connection. For leakage-free sealing the ball then bears sealingly on the valve seat.
It is further known (DE-PS 3,310,785) to hold the spherical valve element of a seat valve in a sleeve of which the end face as onflow face faces the valve seat and which is guided in an axial bore of the housing or of a housing insert. This reliably ensures opening of the valve and the full passage cross-section is opened.
The problem underlying the invention is to provide a seat valve with positive switching overlap.